1. Technical Field
The present invention relates to an ink composition mainly for photo black ink. More specifically, the invention relates to a black ink composition that can realize a neutral black color not only in a reflected color seen from a point a 2-degree angle away from the 45-degree angle specular reflection to a normal illumination at a 45-degree angle, in the direction away from the perpendicular line (bronze color), but also in a visually perceived color (reflected color seen from a point a 20-degree angle away from the 45-degree angle specular reflection to a normal illumination at a 45-degree angle, in the direction away from the perpendicular line).
2. Related Art
Various black ink compositions using a complementary color pigment and enabling a neutral black output have been developed up to now.
British Patent No. 2370580A discloses obtaining a low-saturation black ink composition by adding a phthalocyanine-based pigment as well as a dioxane-based pigment as a complementary color pigment. However, when that black ink composition is applied to a medium having a layer of resin coating, the output is not visually perceived as a neutral black.
U.S. Pat. Nos. 5,803,958 and 6,565,202B2 also disclose a black ink composition using a complementary color pigment. However, the disclosed black ink compositions have the ratio of the complementary color pigment to a carbon black pigment of not less than 0.66, and, as in the one disclosed in the above British Patent, their output is not visually perceived as a neutral black.